81891164 has 12 divisors (see below), whose sum is σ = 143382624. Its totient is φ = 40924704.

The previous prime is 81891151. The next prime is 81891167. The reversal of 81891164 is 46119818.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81891167) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6557 + ... + 14379.

It is an arithmetic number, because the mean of its divisors is an integer number (11948552).

Almost surely, 2^81891164 is an apocalyptic number.

It is an amenable number.

81891164 is a deficient number, since it is larger than the sum of its proper divisors (61491460).

81891164 is a wasteful number, since it uses less digits than its factorization.

81891164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10444 (or 10442 counting only the distinct ones).

The product of its digits is 13824, while the sum is 38.

The square root of 81891164 is about 9049.3736799847. The cubic root of 81891164 is about 434.2558537253.

The spelling of 81891164 in words is "eighty-one million, eight hundred ninety-one thousand, one hundred sixty-four".